Golf balls generally include a spherical outer surface with a plurality of dimples formed thereon. The dimples on a golf ball improve the aerodynamic characteristics of a golf ball and, therefore, golf ball manufacturers have researched dimple patterns, shape, volume, and cross-section in order to improve the aerodynamic performance of a golf ball. Determining specific dimple arrangements and dimple shapes that result in an aerodynamic advantage requires an understanding of how a golf ball travels through the air.
Aerodynamic forces acting on a golf ball are typically resolved into orthogonal components of lift (FL) and drag (FD). Lift is defined as the aerodynamic force component acting perpendicular to the flight path. It results from a difference in pressure that is created by a distortion in the air flow that results from the back spin of the ball. Due to the back spin, the top of the ball moves with the air flow, which delays the separation to a point further aft. Conversely, the bottom of the ball moves against the air flow, moving the separation point forward. This asymmetrical separation creates an arch in the flow pattern, requiring the air over the top of the ball to move faster, and thus have lower pressure than the air underneath the ball.
Drag is defined as the aerodynamic force component acting opposite to the ball flight direction. As the ball travels through the air, the air surrounding the ball has different velocities and, thus, different pressures. The air exerts maximum pressure at the stagnation point on the front of the ball. The air then flows over the sides of the ball and has increased velocity and reduced pressure. The air separates from the surface of the ball, leaving a large turbulent flow area with low pressure, i.e., the wake. The difference between the high pressure in front of the ball and the low pressure behind the ball reduces the ball speed and acts as the primary source of drag.
Lift and drag, among other aerodynamic characteristics of a golf ball, are influenced by the external surface geometry of the ball, which includes the dimples thereon. As such, the dimples on a golf ball play an important role in controlling those parameters. For example, the dimples on a golf ball create a turbulent boundary layer around the ball, i.e., the air in a thin layer adjacent to the ball flows in a turbulent manner. The turbulence energizes the boundary layer and helps it stay attached further around the ball to reduce the area of the wake. This greatly increases the pressure behind the ball and substantially reduces the drag.
Accordingly, the design variables associated with the external surface geometry of a golf ball, e.g., surface coverage, dimple pattern layout, and individual dimple geometries, provide golf ball manufacturers the ability to control and optimize ball flight. However, any adjustments to dimple geometry in an attempt to optimize aerodynamic characteristics have been limited to dimple profile. While the dimple profile has been used by manufacturers in an attempt to affect the aerodynamic performance of the golf ball, the dimple plan shape has remained largely circular in nature. Circular perimeters, however, limit packing efficiency and the number of dimple counts that are achievable for a particular polyhedral base geometry. While non-circular dimple plan shapes have been discussed as alternatives to circular perimeters, see, e.g., U.S. Pat. No. 8,974,320, such discussion is limited to polygonal, teardrop, or elliptical dimples, which still limits surface coverage uniformity and packing efficiency. Accordingly, there remains a need for a dimple plan shape that results in a maximized surface coverage uniformity and packing efficiency, while maintaining desirable aerodynamic characteristics.